# raster data jduh/courses/geog492w12/week3b.pdf · pdf file 1 raster data analysis raster...

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• 1

Raster Data Analysis

Raster Data Model

• Cells (Pixels)

• Cell value

• x, y cell sizes

• Geographic coordinates

Attributes

• 2

Raster to Vector / Vector to Raster

V2R

R2V

ArcGIS Spatial Analyst

• Mainly for raster data analysis

– Arctoolbox: Spatial Analyst Tools

– Spatial Analyst Toolbar

– Raster Calculator

• 3

Raster Calculator • Single-line map algebraic expression

• Multiple inputs in a single expression.

• Multiple Spatial Analyst tools in a single expression.

Raster Calculator Syntax

• Operators inraster1 + inraster2

• Tools & Functions (tool names are case sensitive!) Aspect("C:/Datat/inraster")

• Tool parameters Slope(“dem”, "PERCENT_RISE")

• 4

Spatial Analyst Option Menu (ArcGIS 9.x)

Geoprocessing Environment Setting (ArcGIS 10)

• 5

Raster Calculator Functions

• Arcinfo

Workstation /

Arcdoc

• > 200 functions

• 6

Raster Operations

Local operation

(majority)

Focal operation

(focalmajority)

Zonal operation

(zonalmajority)

Global operation

(costdistance)

Application functions

• 7

Local Operator: Combine

• 8

Working with Nodata in RC

• ISNULL: convert Nodata to a value

• SETNULL: set cell value to Nodata

• CON: conditional function

• Examples

– Replace Nodata with 0 in a DEM

con(isnull([dem]), 0, [dem])

– Set slope > 15 to Nodata on the DEM

setnull([slope]> 15, [dem])

• 9

ISNULL() Function

SETNULL() Function

• 10

CON() Function

Raster Clip Example

Output A Output B Output C

• 11

Raster Clip

• 12

Raster Buffering

Point Features to Raster

• Con( isnull(pointg), 0, 1)

• 13

• 14

Implementing Ordered Weighted

Average in ArcGIS

• Raster Calculator

r1 = rank(1, [factor1], [factor2], [factor3])

r2 = rank(2, [factor1], [factor2], [factor3])

r3 = rank(3, [factor1], [factor2], [factor3])

owavg = [r1] * 0.5 + [r2] * 0.3 + [r3] * 0.2